Party-line lockout for telephone systems



J. W DORS'EY.

PARTY LINE LOCKOUT FOR, TELEPHONE SYSTEMS.

APPLICATION mmwnc'zo. 1917.

Patented June 28, 1921.

'vwen r01 Rin er Br/btge Test Bridge Signaliry Bridge attozneq UNITED STATES PATENT OFFICE...

JOHN w. DORSEY, or WINNIPEG, ANIT'QBAQCANADA PARTY-LINE; LOCKOUT Eon- TELEPHONE SYSTEMS.

To all whomit may concern: I

Be it known that I, JOHN W DOI l SEY, a citizen of the United States, residing at Winnipeg, in the Province of Manitoba, 1n the Dominion of Canada, have invented new and useful Improvements in Party-L ne Lockouts for Telephone Systems, of which the following is a specification.

My invention relates to telephone systems and has for its object the provision of a simple party-line lockout and signal ngdevice for use in common battery substation circuits.

Stated in general terms, I attain my object by providing atest relay bridged across the line by the subscriber in initiating a call, this relay becoming energized if the line is idle, to connect the talking .set' in parallel with itself across the line. The relay armature is provided with a signalmg means, whereby the calling subscriber is audibly informed if the line is clear; and a key and supplemental signaling device are alsoprovided whereby a Subscriberalready on the line may call anothersubscriber on the same line. In a typical circuit, the ringer, the test relay, the talking set, and the auxiliary signaling device are in parallel bridges, the last three controlled by the switch-hook and the special signaling key; and the circuit is sc -designed. that in applying it to a desk set, not more than three conductors need be used in the cord.

My invention is illustrated in'the' accompanying drawings in which Figure 1 is a diagrammatic view of a substation equipped with my improved lockoutsystem. V f

- Fig. -2 is a modified .arrangement of the apparatus using-the same circuitarrange- V ment.

Fig. 3 is a diagramof the invention applied; to 'a system. using selective ringing.

V Fig. 4 is a dia ram. showing my invention applied to the Iell0gg ubstation circu t. Fig. 5 is a diagram showing the theoretical circuit arrangement, the diiferent bridges being indicated by legends thereon.

Referring to the drawings in detail and first to Figs. 1 to 3, these show the invention applied in different ways to theVVestern Electric type of substation circuit. In Fig. 1 the line wires 1 and 2 of a common battery exchange ystem extend to a plurality of branch station lines as indicated so arranged that the armature Specification of Letters Patent. Patented J 28 1921 Application filed J'une 20, 1917. Serial No. 175,798. i

paratus and circuit arrangement at each station is the same, only one will be here shown "and described. The substation apparatus consists of the usual switch-hook H, recelver R, transmitter T, induction coil I, talking and ringing condensers C and C, and a rlnger Q of any type responsive to a fluctuating or interrupted current, and in addltion to these usual apparatus elements, I provide a combination signal and cut-in relay S, vibrator V, and control key K. The relay S is a potential relay wound, preferably, to about 3,000 ohms or'of such resistance as to make the drop across the line substantially negligible when connected thereacross, its required resistance therefore depending upon the voltage .of the, system in whlch it is used, the present arrangement being for a system using about 20 volts at the exchange. The relay S is provided-with a vibratory spring'armature 7 normally disengaged-from the contact 8, the parts being will con tmue to vibrate for an appreciable time after it has been thrown into engagement with the contact 8 upon -the energization of the relay.

The circuit connections are as follows:

Theringer Q is normally connected'across the line in series with. the condenser C through the branch. line 3'4. The relay S is arranged to be connected in bridge of the line through the switch-hook contact 9 upon raising of the switch-hook H. This connection may be traced as follows Line wire 1, branch wire 3, relay S, conductor 10, binding post 11, cord conductor 12,'binding post 13, switch-hook contact 9, switch-hook H,"

binding post 14, cordconductor 15, binding post 16, and conductor aback to line wire 2. The normallyclosed contact 17 of the key K and the normally openrelay contact 8 control the connection of the transmitter T across the line in series with one winding of the induction coil I. The connection may be traced from line wire 1, branch 3, armature 7, contact 8, contact 17, induction coil I, conductor 18, conductor 19, transmitter T, contacts of switch-hook, binding post 14, cord conductor 15, binding post 16, branch conductor 4, and back over line wire 2. The normally open contact 19 of the key K is connected to control the connection of the vibrator V in bridge of the line and in series with the contact 8 of the relay S,

which circuit may be traced from line wire 1, over branch conductor 3, armature 7 contact 8, contact 19, vibrator V, and back through branch line 4 to the other side of the main line 2. q

The operation is as follows: The sub.- scriber on the branch line 3-4, desiring a connection with the substationon the branch line 5-6, raises his receiver from the hook which connects the relay S in bridge of-the main line over the'circuit previously traced, If at this moment the line is idle, the voltage acrossthe line conductors 12 will be sufliciently high to energize the potential relay S which upon energization attracts its arma-' ture 7 into engagement with the contact 8, the armature continuing to vibrate for an appreciable length of time. The engagement'of the armature 7 with the contact 8 completes the-calling subscribers battery supply circuit which is the same as that previously described for the connection of the transmitter T in bridge of the line, and the armature 7 continuing tovibrate, sets up fluctuations'in the supply circuit in unison with its vibrations, giving the subscriber a signal through his receiver which indicates to him that the line is idle. This connection of the transmitter 'circuitacross the line causes a substantial drop in voltage which in practice-with a system of- 20 volts,"brings' the potential across the line down-to, about onevolt,-which, however, is amply suflicient tohold'the relay S energized, its armature having already been attracted and the air gap reduced to a minimum. The closure'of the line circuit signals the operator at the central station in the usual manner and through the usual line terminal apparatus, and the operator connecting in on the line in response to this signal causes an increase in;

the line potential which in practice is found to come to about 6 volts. The subscriber on the branch line 3 4: now signals the desired substation by actuating the keyK to close. the contact 19 and open the contact 17 The opening of thecontact 17 disconnectsthe heavy circuit of the transmitter. from ,the line and connects the vibrator V. in bridge 'ofthe, line over the circuit previously de scribed. As the'transmitter circuit is now removed from the line, the voltage thereacross is influenced onlyby the'drop across,

the -terminals of the relay S and the vibrator V, the drop due to the connection of the relay S being negligible, while the vibrator V isso wound as to bring the'line voltage,

down to the minimum required to hold the relay S energized, which in practiceis found tobe'about one volt. Each time the vibrator opens'its' circuit,"the'line is opened except for the relay S so that the actuation of the vibrator produces a fluctuation of the line potential which in practice is. found to be from about 1 to 20 volts. I The ringers Q and condensers C 'ofall the branch circuits respond to these fluctuations, the particular subscriber desired being selected by means of the'usualcode' signal whichrthe calling l subscriber is enabled to give by suitable op- ;eratio n of the calling key Kr The party on branch line 56, responding to the call, 7

-with the main line 1+2 for conversation thereover, both parties beingfsupplied' with current from the common battery central station.

Should the main line be'busy, due to the connection of one of the substations therewith, when a second or third party attempts to connect with the line by raising his receiver from the switch-hook, the high-resist ance relay S will become connected across the line. but will notbecome energized to attract its :armature due to the substantial drop in-voltage caused by the connection of the heavy transmitter circuits or circuit of the other branch lines or'line across themain line. Thus a second orcthirdparty coming onto the lineafter another partyhas raised hisreceiver to ma-kefa call or after two other parties have become connected for conversation, will not receive the idle signal and so will be. aware that the line-"is-already in use." Itis to be pointed out here, however, that when the second party raises his receiver response to a call from a partyj previously connected to; the line and' at the moment operating his lyibratorV, the relay S of the, answering subscriber will become. energized during one of the interruptionperiods of the.

here shown the combination 7 tions of form andarrangement as fall. within J the scope-'ofthe appended claims arefcontemplatedby me. c

' In'the apparatus arrangement of'Fig. 1, I

have shownall the apparatus tojthefrig ht of the dotted line as mounted in the usualwall box with four conductors 20, 21, 1 2'and15/ leading therefrom to the usual desk set indi-g cated to the'left of the dotted'line and consisting of the switch-hook, transmitter and receiver, the conductors 20, 21, 12 and 15 it representing the usual flexible cord or cable. In the arrangement of Fig. 2, the apparatus shown to the right of the dotted line, is mounted in the wall box while that shown to the left is carried by the desk set. With thls arrangement only three conductors are required. in-the flexible cable between the wall boxandde'sk set. The 'difierence between Figs. 1 and 2 lies/only in thepositioning of the apparatus elements, the circuit arrangement being identically the same.

The arrangement shown in Fig. 3 is .the same as -that of Fig. 2. with'the exception thatthe vibrator V and signal control, key Kare omitted and the signaling effected by meansof any suitable selective ringing systemcontrolled from the centraloflice; N

In Fig. 4, the invention isshown applied to theKellogg substation circuit. Herethe arrangement excluding the talking circuit, is-the same as thatofFig. 2, that is, the relay S is connected in bridge of the line and in serieswith the normally open switchhook contact,.the vibrator V is connected in bridge of the line and in series with the normally open contact 19 of the key. K and the contact 8 of the relay S, and the battery supply or transmitter circuit is connected across the line in series with the normally open switch-hook contact, key contact 17 and relay contact 8.

From the foregoing it will be seen that I have provided an effective lockout and signal system with the addition only of a simple relay, key and vibrator to an existing type of substation circuit, and an eflective lockout system with the use only of a novel and simple form of relay in addition to an existing type of substation circuit and selective ringing system for example as the embodiment shown in Fig. 3.

Having thus described my invention what I claim and desire to secure by Letters Patent is 1. In a common battery telephone ex change system a combined party line lockout and signaling system for installation at the substation only, comprising a potential relay controlling the talking circuit of its associated substation and arranged to be,

connected in bridge of the line upon raising of the switch-hook, means energized from the central station for effecting a rapid fluctuation of the potential across the line above such minimum as will hold said potential relay energized, said potential varyable, and signaling means responsive to said Y potential fluctuations.

2. A party line lockout system compris ing, at each substation, a potential relay normally holding the talking circuit open and responsive to the closing ofthe switch-hook contacts'to close thetalkingvcircuit and pro: duce current fluctuations therein for an appreciable time, 7 v

3. A' combi ed partly 'line lockout and signaling system for installation at the substation only, comprising a potential relay controlling thetalkingcircuit of its associatedsubstation and arranged to be connectedfin bridge ofthe line upon raising of the switch-hook, means for efi'ecting a rapid fluctuation of'the potential across the line above theminim'um required to hold said potential relay energized, said potential varying means being arranged to be operable only during the energization of said relay, signal to open the talking circuit and render said potential varying meansoperable, and signalingv means responsive to' said potential fluctuations, said relay being arranged to produce current variation in the talking circuit-during an appreciable time after the closure thereof, I v f 4; Ina party-line telephone system, a line circuit, a ,source of current therefor, a talk ing set, a test relay controlling the connection of the talking set with the line' and responsive to current in the line when the line is clear, only, a switch hook controlling the connection of the relay to the line, and means actuated by said relay in its operation to produce current fluctuations in the talking circuit for an appreciable length of time, whereby the calling subscriber 1s apprised of the line conditlon by a sound or by silence, as the case may be.

5. In a party-linetelephone system, a line circuit, a source of current therefor, a talking set, a test relay controlling the connection of the talking set with the line and responsive to maximum potential only due to said source, a switch hook controlling the connection of the relay to the line, and means actuated by said relay in its operation to produce current fluctuations in the talking circuit for an appreciable length'o'f time, whereby the calling subscriber is apprised of the line condition by a sound or by silence, as the case may be.

6. In a central energy party-line tele-. phone system, a line circuit, and a plurality of bridged stations on the line, a signal receiving device such as a polarized ringer, a talking bridge and a high resistance test relay bridge at each station, a switch hook controlling the relay bridge, the relay controlling the talking bridge, a vibrator bridged direct across the line, and a key with normally closed contacts in the talking bridge and normally open contacts in said vibrator bridge.

7. A party line lockout substation equipmentcomprising a talking set, a ringercondenser and a test relay, a talking circuit controlled by said relay, a switch hook on controlling means operable by the subscriber said talking set controlling the circuitof said relay,and a flexible cord which containsnotmore than three Wiresconnecting said talking set Withsaid ringer-condenser and relay," i I 8. In". a telephone system employing a common source of "direct current at the central station, a party-line circuit, signaling means at each subscribers station? on the party-line comprising a Polarized receiving device normally responslve toi alternating current,.a condenser in series therewith, a vibrator at each subscribers station arranged to be energized from a'central station, and operable over the line to charge and discharge said condenser through said ringing means. v 9. I In acentra l energy telephone exchange v system, a party-line, a plurality of sub-stations on said line, each sub-s'tation having a vpolarized ringer and a condenser connected in series across-the line, a high resistance relay bridged across the line and controlling the talking circuit and means energized by direct current from the central station operable to rapidlly connect and disconnect a low resistanoe in hridge of the line, whereby a fluctuation ofmntial on the line above the minimum required to holdsaid high resistance relay energized efi'e'cted Withthe result that the condenser is charged'and the ringer;

discharged series cuit for centralized energy telephone'ex change systems, comprising an induction coil, receiver, transmitter and switch hook, theprimary'winding of said indu tion coil 10. A arty line lockout sub-station iiand the transmitter being connected in se-f v ries, the secondary Winding of the induction coil, the receiver and a, condenser being connected in series with each other and *in shunt across the transmitter, a single pair of contacts controlled by said switch hook 

